Assessment of natural and hybrid ventilation models in whole-building energy simulations

Natural ventilation is a traditional cost-effective technique to cool and ventilate buildings. Proper simulation tools are highly desired to ensure acceptable thermal performance of naturally ventilated buildings and to assist the design and optimization of such buildings. This study is to advance the use of natural and hybrid ventilation concepts in building design by assessing the accuracy and usability of current thermal-ventilation models. Because of the similarity noted among various models and tools, a prevalent airflow-thermal modeling program, EnergyPlus, was evaluated by simulating three selected real buildings that were supplied with most detailed building and measurement information. The study of these cases reveals that the current model has (1) significant functional limitations for venting and exhaust fan control schemes; (2) need for additional relationships to describe horizontal openings and fully-open connections between zones; and (3) possible over-prediction of buoyancy-driven flows in the case of multi-story buildings. The study further indicates the building and measurement data that are critical for a more accurate validation of thermal-ventilation models, including, on-site measured temperature, wind, and solar conditions; measured volume flow rate data, at critical points throughout the building; and effective area and discharge coefficients for specific vents used in building.

• Assess accuracy and usability of current thermal-airflow models.
• Model three real buildings against measurement.
• Indicate the deficiencies of the current models.
• Highlight the critical measurement data for more accurate validation of models.